Master node, secondary node, and methods therefor

Abstract

A master node (MN) ( 1 ) controls the MN ( 1 ) to enable, for a radio terminal ( 3 ), dual connectivity using a Master Cell Group (MCG) provided by the MN ( 1 ) and a Secondary Cell Group (SCG) provided by a secondary node (SN) ( 2 ). The MN ( 1 ) sends to the SN ( 2 ) a first message related to a modification or release of a configuration or resource in the SN ( 2 ) regarding the dual connectivity. The first message explicitly or implicitly indicates that the modification or release is related to a failure of the MCG or recovery from the failure of the MCG. This, for example, allows the SN to distinguish a message regarding modification or release of an SN configuration (or resource) sent from an MN to the SN for recovery from an MCG failure from other messages.

What is claimed is: 
     
       1. A method for a Secondary node of a dual connectivity with a Master node, the method comprising:
 communicating, with a user terminal, using a Secondary Cell Group (SCG), which is a group of serving cells associated with the Secondary node; 
 receiving a Radio Resource Control (RRC) Transfer message from the Master node if radio link failure is detected for a Master Cell Group (MCG) which is a group of serving cells associated with the Master node, the RRC Transfer message including a Packet Data Convergence Protocol control-plane (PDCP-C) Protocol Data Unit (PDU) encapsulating a RRC Reconfiguration message, the RRC Transfer message including, in addition to the RRC Reconfiguration message, information indicating to the Secondary node that the RRC Reconfiguration message relates to a recovery of the MCG failure; and 
 transmitting the RRC Reconfiguration message to the user terminal before a release of resources. 
 
     
     
       2. The method according to  claim 1 , further comprising receiving a Release Request message from the Master node. 
     
     
       3. The method according to  claim 2 , further comprising releasing the resources based on the Release Request message. 
     
     
       4. A method for a Master node of a dual connectivity with a Secondary node, the method comprising:
 communicating, with a user terminal, using an MCG, which is a group of serving cells associated with the Master node; and 
 transmitting a RRC Transfer message to the Secondary node if radio link failure is detected for the MCG, the RRC Transfer message including a PDCP-C PDU encapsulating a RRC Reconfiguration message, the RRC Transfer message including, in addition to the RRC Reconfiguration message, information indicating to the Secondary node that the RRC Reconfiguration message relates to a recovery of the MCG failure, 
 wherein the RRC Reconfiguration message is transmitted to the user terminal before a release of resources. 
 
     
     
       5. The method according to  claim 4 , further comprising transmitting a Release Request message to the Secondary node. 
     
     
       6. The method according to  claim 5 , wherein the Release Request message causes the Secondary Node to release the resources based on the Release Request message. 
     
     
       7. A Secondary node of a dual connectivity with a Master node, the Secondary node comprising:
 at least one memory; and 
 at least one processor coupled to the memory and configured to:
 communicate, with a user terminal, using an SCG, which is a group of serving cells associated with the Secondary node; 
 receive a RRC Transfer message from the Master node if radio link failure is detected for an MCG which is a group of serving cells associated with the Master node, the RRC Transfer message including a PDCP-C PDU encapsulating a RRC Reconfiguration message, the RRC Transfer message including, in addition to the RRC Reconfiguration message, information indicating to the Secondary node that the RRC Reconfiguration message relates to a recovery of the MCG failure; and 
 transmit the RRC Reconfiguration message to the user terminal before a release of resources. 
 
 
     
     
       8. The Secondary node according to  claim 7 , wherein the at least one processor is further configured to receive a Release Request message from the Master node. 
     
     
       9. The Secondary node according to  claim 8 , wherein the at least one processor is further configured to release the resources based on the Release Request message. 
     
     
       10. A Master node of a dual connectivity with a Secondary node, the Master node comprising:
 at least one memory; and 
 at least one processor coupled to the memory and configured to:
 communicate, with a user terminal, using an MCG, which is a group of serving cells associated with the Master node; and 
 transmit a RRC Transfer message to the Secondary node if radio link failure is detected for the MCG, the RRC Transfer message including a PDCP-C PDU encapsulating a RRC Reconfiguration message, the RRC Transfer message including, in addition to the RRC Reconfiguration message, information indicating to the Secondary node that the RRC Reconfiguration message relates to a recovery of the MCG failure, 
 
 wherein the RRC Reconfiguration message is transmitted to the user terminal before a release of resources. 
 
     
     
       11. The Master node according to  claim 10 , wherein the at least one processor is further configured to transmit a Release Request message to the Secondary node. 
     
     
       12. The Master node according to  claim 11 , wherein the Release Request message causes the Secondary Node to release the resources based on the Release Request message.